I have the mold for making one of those. It was turned by Art Reed about five years ago. A couple friends helped me blow a few for a matching pair. Mold is only 3/4 of the piece, then it gets puntied and opened up to the right diameter for the lip. I think the originals were bonked off the pipe then popped. It's a pain in the ass kind of job that's usually not quite enough money for the labor. The mold was dried really slowly and doesn't look out of round but who knows once it's wet again.